1. Field of the Invention
The present invention relates to a system and a method for making use of rainwater falling on and collected at houses and buildings.
2. Description of the Related Art
In general, the volume content or the filling ratio of water molecules in water is at most about 34%. To this end, water is compared to sponge having a number of air gaps in it. Since water molecules are chemical compounds consisting of oxygen and hydrogen, they attract both cations (positive ions) and anions (negative ions), and trap various substances in the gaps among the water molecules.
Water is categorized as a solvent with a property of dissolving materials very well. On the other hand, most materials existing on the earth are categorized as solutes that are soluble in water. As commonly understood, xe2x80x9cwaterxe2x80x9d, including the tap water, is a mixture of solvent (i.e., a gathering of water molecules) and solutes, such as minerals.
xe2x80x9cPure waterxe2x80x9d is artificial water, which is produced by physically filtering water, i.e., a mixture of water molecules and various solutes, and removing such solutes and impurities. Pure water has a high absorbency, which is an essential element of its function as a solvent. Pure water is called xe2x80x9chungry waterxe2x80x9d because of its absorbency, and is used to rinse IC substrates because of its cleansing ability. Pure water is also used as a raw material for drinking water and various beverages because it contains few impurities or solutes. Thus, pure water has been broadly applied to various uses in these years.
While pure water is an artificially filtrated product, rain and snow are products of the nature and closest to pure water because they are gatherings of pure water molecules evaporating in the atmosphere.
The quantity of solutes contained in a unit volume of water is expressed as hardness. The hardness of tap water in Japan is about 70 mg to 170 mg per liter, and is categorized as soft water containing few solutes by global standards. The hardness of tap water in mountainous areas of Europe is about 370 mg to 400 mg per liter, and is categorized as hard water. The hardness of rainwater is much lower even than soft water, at less than 20 mg per liter. This means that rainwater is supersoft water containing little solute and extremely close to the gathering just of water molecules that is, pure water.
The less solutes contained in water, the easier it is to filtrate or purify, and the more possible to treat without using harmful chlorine or other chemicals. Accordingly, rainwater can be recycled into safe natural water. Such recycled rainwater is superior in absorbency, and has a broad range of uses, including rinsing water or drinking water. As long as a reliable filtering means is used and the quality of rainwater is guaranteed, rainwater can be optimally used in various ways, including watering garden plants, washing cars, sanitary water, kitchen water and drinking water.
However, with the conventional techniques, rainwater has not been positively or practically utilized, in spite of its superior nature and possibility as the optimum living water. So far, rainwater has only been treated as wastewater, and recycling of rainwater has not been considered sufficiently.
Therefore, it is one of the objectives of the present invention to reevaluate the properties of rainwater, and to provide a system and a method that can positively utilize rainwater collected at houses and buildings, making the best use of this natural resource.
To achieve the objective, rainwater is collected form the roof surface of a building or a house through a gutter. A predetermined amount of initial precipitation is removed or thrown away, and the subsequent rainwater is treated (e.g., purified) and stored in a storage tank. The purification includes pH adjustment and sterilization of the rainwater. The stored rainwater is then taken out of the storage tank by, for example, pumping for actual use.
In another method of utilizing rainwater, rainwater is collected from the roof surface of a building or house through a gutter. A predetermined amount of initial precipitation is removed or thrown away, and the subsequent rainwater is supplied to a purifier, in which the rainwater is subjected to pH adjustment and sterilization. The purified rainwater is supplied to a storage tank. The water level of the storage tank is monitored, and if the water level reaches the prescribed upper limit, the rainwater is prevented from entering the purifier or the storage tank.
In still another method of utilizing rainwater, rainwater is collected from the roof surface of a building through a gutter. A predetermined amount of initial precipitation is removed or thrown away, and the subsequent rainwater is supplied to a purifier, in which the rainwater is subjected to pH adjustment and sterilization. The purified rainwater is then supplied to a storage tank. The water level of the storage tank is monitored, and if the water level reaches the prescribed lower limit, a predetermined amount of tap water is supplied to the storage tank in order to keep the water level at a certain level.
The second and third methods may be combined. In this case, those steps up to the supplying the purified rainwater in the storage tank are the same. Both the upper and the lower limits of water level of the storage tank are monitored. If the water level reaches the prescribed upper limit, no more rainwater is supplied to the purifier or the storage tank, and if the water level reaches the prescribed lower limit, a predetermined amount of tap water is supplied to the storage tank.
In any one of the above-described methods, rainwater is subjected to a prescribed physical filtration at or before the inlet port of the purifier. The purification step includes neutralization of acid rainwater by, for example, pH-adjustment, and sterilization using active oxygen species (or free radicals) produced by decomposition of aqueous hydrogen peroxide.
Preferably, the residual active oxygen species remaining in the purified rainwater is decomposed or eliminated in the storage tank using, for example, secondary reactive catalyst.
Preferably, before the purified rainwater is supplied from the storage tank for indoor use, an active charcoal filter and a sediment filter further filter the purified rainwater.
In another aspect of the invention, a system for utilizing rainwater falling on buildings and houses is provided. The system comprises a means for removing a predetermined amount of initial precipitation from rainwater collected from the roof of a building through a gutter, a purifier including a filter and a sterilizer, and a storage tank for storing the purified rainwater. The purifier receives rainwater, from which the initial precipitation has been removed. The filter of the purifier filters the rainwater physically, and adjusts the pH value of the filtered rainwater. The sterilizer sterilizes the filtered and pH-adjusted rainwater using active oxygen species (i.e., free radicals) produced by decomposition of aqueous hydrogen peroxide.
Another type of rainwater utilization system comprises an initial precipitation collection tank, a purifier including a filter and a sterilizer, a switching valve, a storage tank for storing purified rainwater, and a level sensor for sensing the water level of the storage tank. The initial precipitation collecting tank temporarily stores a predetermined amount of initial precipitation of the collecting from the roof of the building. The filter of the purifier carries out physical filtration and pH adjustment, and the sterilizer sterilizes the filtered and pH-adjusted rainwater using active oxygen species (i.e., free radicals). The switching valve switches the water path between the initial precipitation collection tank and the purifier. To be more precise, if the water level of the initial precipitation collection tank reaches a predetermined level, the switching valve closes up so that no more rainwater flows into the initial precipitation collection tank, and instead, that the subsequent rainwater flows into the purifier. The level sensor provided to detect the water level of the storage tank is connected to and cooperates with the switching valve. If the level sensor detects that the water level of the storage tank has reached the upper limit, it causes the switching valve to switch the water path and guide the rainwater into the initial precipitation collection tank.
Still another type of rainwater utilization system comprises an initial precipitation collection tank, a purifier, a storage tank storing purified rainwater, a tap-water supply pipe equipped with a tap-water supply valve, and a level sensor for sensing the water level of the storage tank. The initial precipitation collection tank temporarily stores a predetermined initial amount of rainwater collected from the roof of a building through a gutter. The purifier receives the subsequent rainwater after the initial precipitation has been removed into the initial precipitation collection tank. The filter of the purifier carries out physical filtration and pH adjustment, and the sterilizer sterilizes the filtered rainwater using active oxygen species (i.e., free radicals). The level sensor is connected to and cooperates with the tap-water supply valve. If the level sensor detects the water level of the storage tank having reached the prescribed lower limit, it causes the tap-water supply valve to open in order to supply a predetermined amount of tap water into the storage tank.
Still another type of rainwater utilization system is provided, which detects both the upper and the lower limits of the water level of the storage tank to adjust the water flow in the system. The system comprises an initial precipitation collection tank, a purifier including a filter and a sterilizer, and a storage tank for storing purified rainwater, as in the above-mentioned systems. This system also comprises a first valve for switching the water path between the initial precipitation collection tank and the purifier, and a second valve provided to a tap-water supply pipe extending from the storage tank. An upper limit level sensor is connected to the first valve, and a lower limit level sensor is connected to the second valve. If the upper limit level sensor detects that the water level of the storage tank has reached the prescribed upper limit, it causes the first valve to switch the water path from the purifier to the initial precipitation collection tank. Upon switching the water path, the rainwater collected from the roof flows into the initial precipitation collection tank, and no more rainwater flows into the purifier. If the lower limit level sensor detects that the water level of the storage tank has reached the prescribed lower limit, it causes the second valve to open in order to supply the tap water into the storage tank. By filling the storage tank, which is short of water, with the tap water, the water level of the storage tank is kept at a desired level.
In the above-described systems, the initial precipitation collection tank may have a timer and a drainage valve in order to drain the initial portion of rainfall away from the tank after a prescribed time period.
Preferably, the filter has a physical filtration screen for filtering the rainwater collected from the roof, and a pH-adjusting agent for adjusting the pH value of the rainwater for neutralization because the collected rainwater is generally acidic. The sterilizer contains aqueous hydrogen peroxide and a primary reactive catalyst in order to produce active oxygen species (i.e., free radicals) through decomposition of the hydrogen peroxide. The active oxygen species are used to sterilize the filtered rainwater.
The storage tank contains a secondary reactive catalyst that reacts with the active oxygen species (i.e., free radicals) remaining in the purified rainwater supplied from the purifier, and that decomposes or eliminates the residual active oxygen species. In the reaction, the secondary reactive catalyst decomposes organic substances, while producing oxygen.
Preferably, the storage tank consists of multiple interconnected units or barrels. The number of units is selected depending on how much purified water is required to be stored. The storage tank is placed in the basement or buried in the ground.
In the system that has both upper and lower limit level sensors, a back-up sensor is further furnished to the system. The back-up sensor is placed slightly higher than the upper limit level sensor, and is connected to both the switching valve (i.e., the first valve) and the tap-water supply valve (i.e., the second valve). If the upper limit level sensor is out of order, the back-up sensor detects the water level of the storage tank, and carries out the same operations as the upper limit level sensor. Namely, the back-up sensor causes the switching valve to shut off the water path to the purifier, and allows the rainwater to flow into the initial precipitation collection tank.
The upper limit level sensor is also connected to the tap-water supply valve. When the tap water is supplied to the storage tank because of the shortage of the purified rainwater, the upper limit level sensor detects the elevating water level, and causes the tap-water supply valve to close when the water level reaches the upper limit. As was mentioned above, if the upper limit level sensor is out of order, the back-up sensor detects the elevating water level, and causes the tap-water supply valve to close. In this manner, the water level of the storage tank is kept in the desirable range.
The system has a pump for pumping the purified rainwater from the storage tank for various uses. Preferably, an activated charcoal filter and a sediment filter are provided at or after the outlet port of the storage so that the purified rainwater is further filtered before being used indoor.